Pump assembly for a vehicle braking system with eccentric drive actuator

ABSTRACT

A hydraulic pump assembly  20  of a vehicle braking system includes at least one pair of hydraulic pumps for pumping brake fluid. Each pump  13  has a pump member  14 . The pump members  14  of a pair of pumps are disposed in opposing, spaced relation along an axis. An eccentric drive actuator  22  is disposed between the pump members  14  of a pair of pumps so as to move the pump members substantially simultaneously along the axis between first and second positions.

This application is based on U.S. Provisional Application No.60/651,808, filed on Feb. 10, 2005 and claims the benefit thereof forpriority purposes.

FIELD OF THE INVENTION

The invention relates to a vehicle braking system and, moreparticularly, to an eccentric drive actuator that permits two hydraulicpump members to be actuated simultaneously to pump a hydraulic fluid.

BACKGROUND OF THE INVENTION

With reference to FIG. 1, a conventional hydraulic vehicle brake systemis shown generally indicated at 10. The system 10 includes a motor/pumpunit with an electric motor having a shaft 12 and a hydraulic pump 14for delivering brake fluid. The functionality of the hydraulic system 10is based on fluid flow and pressure. These two characteristics aredependant on the actuation of at least two pump members 14 and 14′ thatare diametrically opposed, as shown in FIG. 1. The linear pump actuationis commonly solved with the use of a centrally located eccentric motionthat drives the pump members 14 one at a time in the directions E. Thismotion is accomplished with the use of a centrally located eccentricbearing 16. This eccentric motion causes one of the pump members 14 tobe actuated or displaced while the other pump member 14′ is released tobe retracted into a pump cylinder cavity.

With this pumping motion, the fluid at the inlet of a hydraulic systemis being pressurized and passed through the system to apply properbraking force to wheels of a vehicle. For adequate pressure and fluidflow the degree of eccentricity is varied on the bearing or shaft end.With the conventional system 10 of FIG. 1, the motor sees high forcesthat create a bending moment on a shaft 12 with each rotation.

There is a need provide a rotating apparatus that actuates bothhydraulic pump members of a vehicle braking system substantiallysimultaneously so as to reduce stress on a motor shaft.

SUMMARY OF THE INVENTION

An object of the invention is to fulfill the need referred to above. Inaccordance with the principles of the present invention, this objectiveis achieved by providing a hydraulic pump assembly of a vehicle brakingsystem that includes at least one pair of hydraulic pumps for pumpingbrake fluid. Each pump has a pump member. The pump members of a pair ofpumps are disposed in opposing, spaced relation along an axis. Aneccentric drive actuator is disposed between the pump members of a pairof pumps so as to move the pump members substantially simultaneouslyalong the axis between first and second positions.

In accordance with another aspect of the invention, a method ofactuating pumps of a vehicle braking system provides at least one pairof hydraulic pumps, each pump having a pump member. The pump members ofa pair of pumps are disposed in opposing, spaced relation along an axis.An eccentric drive actuator is provided between the pump members of apair of pumps so as to contact the pump members. The drive actuator ismoved to a first position thereby moving the pump members substantiallysimultaneously along the axis to a first position to cause the pumps topump brake fluid.

Other objects, features and characteristics of the present invention, aswell as the methods of operation and the functions of the relatedelements of the structure, the combination of parts and economics ofmanufacture will become more apparent upon consideration of thefollowing detailed description and appended claims with reference to theaccompanying drawings, all of which form a part of this specification.

BRIEF DESCRIPTION OF THE DRAWING

The invention will be better understood from the following detaileddescription of the preferred embodiments thereof, taken in conjunctionwith the accompanying drawings, wherein like reference numerals refer tolike parts, in which:

FIG. 1 is a schematic illustration of a conventional hydraulic pumpassembly of a vehicle braking system having eccentric bearing thatdrives two pump members one at a time.

FIG. 2 is a schematic illustration of hydraulic pump assembly of avehicle braking system having an eccentric drive actuator provided inaccordance with the principles of the invention, for driving at leasttwo pump members substantially simultaneously to a pumping position.

FIG. 3 is a schematic illustration of the hydraulic pump assembly ofFIG. 2, shown with the eccentric drive actuator moved to a secondposition with the pump members in a non-pumping position.

FIG. 4 is an end view of an eccentric drive actuator of provided inaccordance with the invention.

FIG. 5 is a perspective view of the eccentric drive actuator of FIG. 4.

FIG. 6 is a perspective view of an eccentric drive actuator of theinvention manufactured into rotor shaft.

FIG. 7 is a schematic illustration of the hydraulic pump assembly ofFIG. 3, but shown with a bearing device between the actuator and thepump members.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

With reference to FIG. 2, hydraulic pump assembly of a vehicle brakingsystem is shown, generally indicated at 20, in accordance with theprinciples of the present invention. The system 20 includes at least onepair of hydraulic pumps 13 with each pump 13 having a pump member 14.The pump members 14 of each pair of pumps are disposed in opposing,spaced relation along axis X. Each pump 13 is constructed and arrangedto pump a brake fluid for a vehicle braking system such as an antilockbraking system (ABS) or a Traction Control braking system. As usedherein, “brake fluid” includes any hydraulic fluid that can be used in avehicle braking system. Linear actuation of the pump members 14 in thedirections E (along axis X) is provided by a centrally located eccentricdrive actuator 22. The eccentric drive actuator 22 is coupled to a shaft12 of a motor (not shown) and, upon rotation, actuates both hydraulicpump members 14 substantially simultaneously. The center O of the driveactuator 22 is disposed on axis X. This configuration advantageouslyequalizes the forces that are pressing onto the motor shaft 12.

In the embodiment of FIG. 2, the forces on shaft 12 are equalizedbecause both pump members 14 are subjecting pressure and force to theshaft 12 at the same time. The drive actuator 22 can be attached to arotor (e.g. via shaft 12) of a motor by any of the following (howevernot limited to) methods:

-   -   1) Press fit onto the shaft of the rotor    -   2) Machined surface of the shaft    -   3) Crimped    -   4) Welded    -   5) Bonded

FIG. 4 shows a front view of the eccentric drive actuator 22 and FIG. 5is a perspective view of the drive actuator 22. The shaft 12 (not shownin FIGS. 4 and 5) is received in a central bore 24.

Alternatively, the shaft 12 and drive actuator 22 can be manufacturedtogether as a one-piece member as shown in FIG. 6. It can be appreciatedthat any means of providing the drive actuator 22 and shaft 12 featuresare within the contemplation of this invention.

With reference to FIG. 4, an embodiment of the eccentric drive actuator22 has two side dimensions A and B. Dimension A defines the maximummovement that would be exhibited by the pump members 14 when engaged bythe drive actuator 22. Dimension B defines the minimum or relaxedposition of the pump members 14. The drive actuator 22 is in constantdirect contact with each pump member 14 and causes the axialdisplacement of the pump members 14.

As shown in FIG. 4, with reference to center O, by having dimensionlines C and C′ equal to each other and dimensions lines D and D′ equalto each other, a pump motion is created in which both pump members 14move substantially simultaneously between a first position (FIG. 2)causing the pumps 13 to pump brake fluid and a second position (FIG. 3)stopping the pumping of brake fluid. The dimension lines C, C′, D and D′each extend from a center O of the drive actuator 22 to a point that istangent with the periphery of the drive actuator 22. Thus, C′+C=B andD+D′=A.

With the use of this equal pump drive actuator 22, the stresses that areexhibited on the shaft 12 of the motor are significantly reduced withregard to the tilting or bending moment of the shaft 12 within therotor. The drive actuator 22 may be either fabricated from a solid pieceof material to act as a wear surface when in direct contact with thepump members, or the actuator 22 can be associated with needle/rollerbearings 26 (FIG. 7) that contact the pumping members 14. Alternatively,the pumping members 14 may incorporate the use of a bearing device 26,instead of being associated with a surface of the eccentric driveactuator 22, or the bearing device 26 may be separate from either thepumping members or drive actuator.

The drive actuator 22 provides the following features:

-   -   1. The drive actuator 22 will cause both pump members to move        simultaneously.    -   2. Force equalization will occur on the shaft 12 as a result of        diametrically opposed pressures.    -   3. The drive actuator 22 that moves the pump members 14 in the        hydraulic system for a vehicle braking system is an integral        part of the system.

The foregoing preferred embodiments have been shown and described forthe purposes of illustrating the structural and functional principles ofthe present invention, as well as illustrating the methods of employingthe preferred embodiments and are subject to change without departingfrom such principles. Therefore, this invention includes allmodifications encompassed within the spirit of the following claims.

1. A hydraulic pump assembly of a vehicle braking system comprising: atleast one pair of hydraulic pumps for pumping brake fluid, each pumphaving a pump member, the pump members of a pair of pumps being disposedin opposing, spaced relation along an axis, and an eccentric driveactuator disposed between the pump members of a pair of pumps so as tomove the pump members substantially simultaneously along the axisbetween first and second positions.
 2. The pump assembly of claim 1,wherein the drive actuator has a center that is disposed on the axis,the drive actuator being constructed and arranged to be rotated andhaving a long side of a certain dimension and a short side of adimension less than the certain dimension, the long and short sides ofthe drive actuator being constructed and arranged such rotation of thedrive actuator moves the pump members substantially simultaneouslybetween the first and second positions.
 3. The pump assembly of claim 2,further comprising a shaft, the drive actuator being coupled with theshaft so that rotation of the shaft rotates the drive actuator.
 4. Thepump assembly of claim 3, wherein the drive actuator and shaft areconstructed and arranged as a one-piece member.
 5. The pump assembly ofclaim 3, wherein the drive actuator includes a bore therein, the shaftbeing received in the bore.
 6. The pump assembly of claim 1, wherein thedrive actuator is in direct contact with the pump members.
 7. The pumpassembly of claim 1, further comprising a bearing device between thedrive actuator and each pump member of a pump pair.
 8. A hydraulic pumpassembly of a vehicle braking system comprising: at least one pair ofhydraulic pumps for pumping brake fluid, each pump having a pump member,the pump members of a pair of pumps being disposed in opposing, spacedrelation along an axis, and means, disposed between the pump members ofa pair of pumps, for moving the pump members generally simultaneouslyalong the axis between first and second positions.
 9. The pump assemblyof claim 8, wherein the means for moving has a center that is disposedon the axis, and is constructed and arranged to be rotated, the meansfor moving has a long side of a certain dimension and a short side of adimension less than the certain dimension, the long and short sides ofthe means for moving being constructed and arranged such rotation of themeans for moving moves the pump members substantially simultaneouslybetween the first and second positions.
 10. The pump assembly of claim8, further comprising a shaft, the means for moving being a driveactuator coupled with the shaft so that rotation of the shaft rotatesthe drive actuator.
 11. The pump assembly of claim 10, wherein the driveactuator and shaft are constructed and arranged as a one-piece member.12. The pump assembly of claim 10, wherein the drive actuator includes abore therein, the shaft being received in the bore.
 13. The pumpassembly of claim 8, wherein the means for moving is in direct contactwith the pump members.
 14. The pump assembly of claim 8, furthercomprising a bearing device between the means for moving and each pumpmember of a pump pair.
 15. A method of actuating pumps of a vehiclebraking system, the method includes: providing at least one pair ofhydraulic pumps, each pump having a pump member, the pump members of apair of pumps being disposed in opposing, spaced relation along an axis,providing an eccentric drive actuator between the pump members of a pairof pumps so as to contact the pump members, and moving the driveactuator to a first position so move the pump members substantiallysimultaneously along the axis to a first position to cause the pumps topump brake fluid.
 16. The method of claim 15, further including movingthe drive actuator to a second position to move the pump memberssubstantially simultaneously to a second position to stop pumping brakefluid.
 17. The method of claim 15, wherein the drive actuator is movedby a shaft of a motor.
 18. The method of claim 17, wherein the driveactuator and the shaft are integral.
 19. The method of claim 17, whereinthe drive actuator has a bore and the shaft is fixedly received in thebore.